ES2653767B1 - ELECTRON SENSOR FOR ELECTRONIC MICROSCOPY - Google Patents

Description

ELECTRON SENSOR FOR ELECTRONIC MICROSCOPY

D E S C R I P C I O N

OBJECT OF THE INVENTION

The object of the present invention is an electron sensor for electron microscopy, and a system with a plurality of electron sensors for electron microscopy.

Therefore, the present invention could be framed in the field of sensors to detect electrons used in transmission electron microscopes (TEM), in scanning electron microscopes (SEM) or in transmission scanning microscopes (STEM).

BACKGROUND OF THE INVENTION

Currently, different applications in the field of electron microscopy detect and accumulate electrons to generate images, or energy spectra. These images, or spectra, are used in the study of materials in science and technology.

Specifically, these applications are based on the irradiation of a sample, with accelerated electrons at energies between 2 keV and 400 keV. Although less frequent there are TEM electronic microscopes that operate with accelerated electrons at high energies up to 1.2 MeV.

More specifically, in transmission electron microscopes (TEM), these accelerated electrons pass through the material that makes up a sample, and by means of magnetic lenses, two-dimensional enlarged images of the sample and diffraction patterns are generated (two-dimensional images). On the other hand, in TEM applications of energy loss electron spectrometry (EELS or EFTEM in its acronyms in English) an energy filter manufactured with electromagnetic lenses is used, with which an energy spectrum is obtained (one-dimensional image), or an image filtered in energy (two-dimensional image) with information about the chemical composition of the sample.

In order to obtain images, electron microscopes comprise electron sensors that are manufactured with "pixelated" semiconductors. That is, semiconductors that on the surface where photons, or electrons, impact, comprise a plurality of discrete electronic components. These discrete electronic components are organized as a one-dimensional, or two-dimensional, matrix to detect photons, or electrons, where each discrete electronic component is often referred to as a "pixel". In this way, "pixelated" semiconductors detect by each "pixel" the impact position of an electron, or a photon, in one, or two, spatial dimensions.

Specifically, the "pixelated" electron sensors used in TEM are manufactured with CCD, or CMOS type technology. Particularly, the CCD sensors include in each "pixel" a sensor part in which the electrons and another part of electronic circuitry impinge. Meanwhile, in the CMOS sensors the electronics are distributed in each pixel, so that the electronics are irradiated by the electrons of the electron beam, making it susceptible to damage by irradiation. In both cases, these technologies are sensitive to radiation damage due to the high energies of the electrons used in electron microscopes.

Another problem for these CMOS technologies, or CCD, is that the electrons are absorbed in different directions including the depth and width of the electron sensor. In this way, the effective resolution of the electron sensor is limited, that is, the proximity in which each "pixel" can be placed is defined. This is because if two adjacent "pixels" are too close to each other, when an electron hits a "pixel" it also generates a signal that can be appreciable in the adjacent "pixels". This effect is known as "charge sharing" or "cross-talk". In this way, for these "pixels" to be sufficiently separated and a good spatial resolution can be obtained in electron microscopes, the electron sensor has to be very large.

In order to avoid the first of these problems, that is to say the one related to the sensitivity to the damage by irradiation, TEM usually uses CMOS sensors, or indirect CCDs. In these sensors the electron does not affect directly in the semiconductor but in a scintillator that is optically coupled to the sensor, and that after the impact generates a cascade of photons, that is, these electrons are converted to photons. These low energy photons, within the visible spectrum, are those that are measured in the "pixellated" photon sensor. In return, this indirect detection of electrons converted to photons does not solve the problem of "charge sharing" or "cross-talk" and degrades the operation of the sensor, affecting some of its technical characteristics such as quantum detection efficiency (DQE) and modulation transfer function (MTF). As a result of this, the quality of the images gets worse, and it is necessary to increase the exposure time to form images with an adequate signal-to-noise ratio. This increase in exposure time is counterproductive in examining many sample types, such as biological samples, which are very susceptible to altering their atomic structure during the observation process in an experiment with TEM.

Recently, in order to avoid all these problems, CMOS sensors have been developed for direct use, that is, capable of measuring electrons without the need for photoconversion in transmission electron microscopes. These new CMOS sensors are based on a combination of known techniques such as: the use of submicron manufacturing technologies, "radhard layout" and backlighting to improve the resistance of the electronic circuitry part in the pixels to irradiation damage and to increase the fill factor or "fill factor". As well as technologies of thinning of the substrate of the sensor of electrons to improve the spatial resolution of the sensor, when reducing the problem of "charge sharing".

The "Silicon-on-Insulator" technology is also used, which allows greater thinning of the substrate compared to conventional CMOS technology.

In any of these cases, the thinning process of the electron sensors is complex, and makes the CMOS sensors, or CCD, very fragile. This also reduces the manufacturing yield and makes the process more expensive, and, in spite of the "radhard layout", these CMOS sensors, or CCDs, are still susceptible to radiation damage when using high-energy electron beams, or with high current densities. Therefore, in their application in TEM, they are usually accompanied by additional protection systems to control the irradiation dose.

More specifically, when CMOS sensors, or CCDs, are used to capture images of diffraction patterns, which are usually formed by discrete points distributed in the image with a high electron current density, these sensors are even more susceptible to being damaged by irradiation.

Another type of direct sensors are of the CMOS type, or CCD, hybrids in which to avoid damage by irradiation with electrons, they use a "pixelated" sensor that is separated from the electronic circuitry by means of the "bump-bonding" technique. In this case, the "fill factor", that is, the ratio between the area with "pixels" of the sensor and its total area, is 100%. In addition, the electrons are completely absorbed in the electron sensor so that the electronic circuitry is not damaged by irradiation. Despite this, this hybrid technology is not a conventional technology, the number of pixels is limited due to its own manufacturing technology, and additionally presents problems of "charge sharing" because the sensor can not be thinned, which implies less spatial resolution.

Finally, electron sensors made with SSD technology ("silicon strip detectors") have also been proposed, wherein the surface of the electron sensor perpendicular to the electron beam that impacts it contains a plurality of electrodes extended as parallel silicon bands. and separated from each other to form one, or two layers.In this type of electron sensors the electrons can directly affect the sensor.

In return, this type of SSD sensor reduces the "fill factor" of the electron sensor and its substrate has to be thinned below 50 p.m. in order to have an adequate spatial resolution for electronic microscopes.In addition, they are not manufactured with conventional technology. All this leads to an expensive, complex process that makes the sensor very delicate to be able to break more easily by reducing the "yield" of manufacturing.

A final problem refers to the dynamic range of the "pixelized" electron sensors, that is, the amplitude of the range of intensity values that can be measured in each "pixel". In the sensors that receive the electrons directly an infinite dynamic range can be obtained, counting the number of electrons that impact in each "pixel" in a time interval, but this is not practical when the intensities in a "pixel" are very high since the electronics is not capable of processing the successive impacts with sufficient speed. In such situations, the detectors must be operated in an integrating mode, ie the sum of the load generated by a large number of impacts and not each individual impact is measured in each pixel. This value measured in the integrator mode is an analog value that must be digitized, with a dynamic range that is determined by the number of bits of the analog-digital converter used. In current "pixelated" detectors, each pixel only has an analog-digital converter with a typical 12-bit dynamic range, this range is insufficient in TEM when two-dimensional images of diffraction patterns are taken. As a result, in some pixels of the image the intensities go out of the dynamic range and their real value is not captured.

DESCRIPTION OF THE INVENTION

The present invention describes an electron sensor for electron microscopy performed by an electron microscope, wherein the electron sensor comprises a substrate, with a front plane and a back plane parallel to each other, which is intended to absorb at least one electron from a beam of electrons that crosses a sample and that is generated by the electron microscope, and this electron is capable of generating an electric charge of free electron-hollow pairs (eh) in said substrate.

More specifically, the electron sensor comprises:

- a lateral receiving surface, located on one of the sides of the substrate to receive the electron beam perpendicularly,

- a guard unit, with a lower plane and an upper plane, deposited in the previous plane bordering parallel to at least the lateral receiving surface traversed by the electron beam, to avoid leakage currents at the edge of the substrate,

- a base unit, with a lower plane and an upper plane, deposited in the previous plane following the guard unit, designed to measure the energy of the electrons that impact on the lateral receiving surface,

- an input unit, with a lower plane and an upper plane, deposited in the previous plane between the lower plane of the guard unit and the upper plane of the base unit for detecting the point of entry of the electrons of the beam electrons, - a contact unit, deposited in the posterior plane, and

- an electronic circuitry unit, located next to the base unit and linked to at least the base unit, the contact unit and the input unit, comprising an electric generator and electric circuit.

Wherein, said electric generator generates an electric polarization current, between the anterior plane and the posterior plane, which drags the free electrons generated in the substrate towards the base unit and / or the input unit, and drags the generated free holes at substrate to the contact unit; allowing the electrons and holes to be captured by their respective units and conditioning and processing the free electrons by an electronic circuit comprised in said control unit to form a one-dimensional or two-dimensional image with a greater dynamic range and to measure the energy of the electrons that they form the image.

More specifically, the input unit comprises a series of input electrodes, or "pixels", separated from each other, and the lower plane of the guard unit comprises at least one guard electrode with a plurality of slots suitable for receiving the plane of the series of input electrodes without directly contacting them.

More specifically, the base unit is intended to reduce the "cross-talk" between adjacent input electrodes, as well as to measure the energy of the electrons that impact on the substrate.

Additionally, the upper plane of the base unit comprises a base electrode with a plurality of slots suitable for receiving the lower plane of the series of input electrodes without directly contacting them.

Preferably, the junction zone between the lower plane of the input unit and the upper plane of the base unit comprises an energy measurement unit for increasing the precision of the measurement of the energy of the electrons passing through the series of power units. entry.

Said energy measurement unit comprises a series of energy measurement electrodes.

Preferably, each energy measurement electrode comprises a superposition of measurement electrodes of a substantially oval configuration.

It should be noted that the input unit, the contact unit and the base unit are connected to an electronic circuitry unit by means of tracks deposited on the contact substrate with high electrical conductivity, for example aluminum, gold or polysilicon.

Alternatively, the input unit, the contact unit, the energy measurement unit and the base unit are connected to an electronic circuitry unit by tracks deposited on the substrate of a contact with high electrical conductivity for example aluminum, gold or polysilicon.

More specifically, the base electrode, each input electrode and each electrode of the superposition of energy measurement electrodes are connected, by means of tracks deposited on the substrate of a contact with high electrical conductivity for example aluminum, gold or polysilicon.

Said electronic circuitry unit is remote from the base unit to avoid its exposure to the radiation of the electrons and to the secondary radiation generated in the substrate.

Said electronic circuitry unit allows to measure the impact position and the energy of the electrons of at least two different forms.

The circuitry unit can measure in position counting mode, where it counts how many electrons impact on each input electrode, in this way it can know in which part of the lateral receiving surface the electrons impact and the number of impacts. Additionally, the circuitry unit can measure in position integrating mode, where it adds up the total charge released by the electrons that impact on each input electrode during a given time and knowing in which part of the receiving side surface they have impacted. In both cases, the electrical charge generated in the sensor and that is not captured by the input electrode (point of impact of the electron) is captured by the electrodes of energy measurement and / or by the base electrode. In this way, the "crosstalk" between the neighboring input electrodes in the linear direction of the sensor is reduced.

Additionally, the circuitry unit can measure counting and integrating mode, where it measures the number of electrons that impact on each input electrode knowing which part of the receiving side surface, while integrating, that is, adds the total load liberated by the electrons that impact on each electrode of energy measurement during a determined time.

Alternatively, the circuitry unit can measure in double integrator mode, where it adds the total charge released by the electrons that impact each input electrode and each electrode of energy measurement during a determined time and knowing in which part of the lateral surface of reception the impact takes place.

Preferably, the electrodes of all the units of the posterior and anterior planes of the substrate are made with doping materials diffused in the substrate. More specifically, the diffusions of type "p" dopants or type "n" of the posterior and anterior faces of the substrate respectively and the doping of the substrate constitute an "array" of diodes with pn junctions.

In this way, by means of said circuitry unit, a polarization voltage is applied between the electrodes of the back and front faces of the substrate so that the "diodes" are reverse polarized, creating a zone of depletion in the substrate.

It should be noted that the proposed electron sensor is preferably a linear sensor, ie it is formed by a single line, or vector of electrodes to measure a one-dimensional or two-dimensional image, and allows the energy of the incident electrons to be measured in each pixel of the image.

Preferably, this electron sensor can be manufactured with conventional lithographic techniques and electronic circuitry by means of microelectronic CMOS technology. More specifically, it can be manufactured using standard CMOS technology, so that while in one area of the substrate the electronic circuitry unit is manufactured, at the other end only the units comprising the different electrodes are manufactured.

Additionally, this electron sensor allows its use as a direct "pixelated" detector of the energy filters that are used in energy loss electron spectrometry applications (EELS or EFTEM in its English acronyms). sensor measures the one-dimensional energy spectrum dispersed by the energy filter In the case of EFTEM, the sensor is used to form two-dimensional images in a specific energy range.

Additionally, by having each sensor pixel of several electrodes at different depths (input electrode and energy measurement electrodes) to measure the charge generated by the impact of an electron, it is possible to measure the energy of the incident electron without need to use an energy filter.

In this way, an electron sensor resistant to damage by irradiation is obtained, which can directly measure the electrons that impact on it with a high spatial and energetic resolution.

Also, by having not only one but several electrodes at different depths (input electrode and energy measurement electrodes) in each pixel, it is possible to measure the load generated by the impact of the electrons in a given time (integrating mode) using more than one electrode in each and thus obtain a greater dynamic range of the sensor compared to the existing pixelated detectors.

Another advantage of this electron sensor is that it allows to form said two-dimensional images in a TEM microscope by scanning the electron beam by electromagnetic means and capturing the image line by line. This is a difference with respect to the sensor technologies used in optical imaging or X-ray imaging applications, which are particles with no electrical charge and therefore can not be scanned by scanning the beam by electromagnetic means.

Additionally, said electron sensor being formed by a single line of input electrodes, the problem of "charge sharing" is eliminated in the transverse direction of the sensor.

On the other hand, due to the fact that the lateral reception surface does not contain electrodes, the "fill factor" of the electron sensor design proposed here is 100%, which allows to detect electron impacts between two input electrodes using techniques of Signal averaging between adjacent input electrodes, known as subpixel techniques, and thereby increase the effective resolution of the sensor.

To summarize, this electron sensor is easy to manufacture and allows to generate one-dimensional or two-dimensional images with a greater dynamic range, as well as to measure the energy of the electron with electrodes at different depths of the substrate, without the electronics for control and processing of the Sensor signals are exposed to electron beam irradiation.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of practical realization thereof, a set of drawings is attached as an integral part of said description. where, with illustrative and non-limiting character, the following has been represented:

Figure 1 shows a perspective view of a preferred embodiment of the electron sensor.

Figure 2.- Shows a schematic side view of the preferred embodiment of the electron sensor.

Figure 3a.- Shows a schematic view in detail of the position of the electrodes.

Figure 3b.- Shows a schematic view in detail of the position of the electrodes where an electron beam hits the lateral receiving surface.

Figure 4 shows a schematic view in detail of the electrode connections.

Figure 5a.- Shows a schematic view of a first configuration of several electron sensors placed in parallel.

Figure 5b.- Shows a schematic view of a second configuration of several electron sensors placed in parallel.

Figure 5c.- Shows a schematic view of a third configuration of several electron sensors placed in parallel.

Figure 5d.- Shows a schematic view of a fourth configuration of several electron sensors placed in parallel.

Figure 5e.- It shows a schematic view of a fifth configuration of several sensors of electrons placed in parallel.

PREFERRED EMBODIMENT OF THE INVENTION

In a preferred embodiment of the invention, as shown in figures 1 and 2, the electron sensor (1), for TEM electron microscopy, comprises a silicon substrate (2) that receives perpendicularly, by means of a receiving surface lateral (3), an electron beam (10) from crossing a sample, not represented, to be investigated. Wherein said electron beam (10) is produced by the TEM microscope, and comprises at least one electron with an electric charge and an energy. To form an image (11) the impact and / or energy position of a large number of electrons of the electron beam (10) are measured.

The substrate (2) comprises a rear plane (2p) and a front plane (2a) parallel to each other, and perpendicular to the lateral receiving surface (3). On said back plane (2p) a contact unit is deposited, and on its previous plane (2a) are deposited in order from least to greatest distance with the lateral receiving surface (3): a guard unit, an input unit , an energy measurement unit, a base unit and an electronic circuitry unit (12).

Preferably, the substrate (2) has a thickness between 300 and 600 μm, and is made of slightly doped p-type silicon of resistivity between 2 and 10 kü.

When this beam of electrons (10) hits the lateral receiving surface (3), the electrons in the electron beam (10) lose energy by generating a free charge of electron-hollow pairs (eh) in the electron beam. silicon of the substrate (2). The generation of an electron-hole pair in silicon requires 3.6 eV so that a single electron of 100 keV that impacts the lateral receiving surface (3) generates approximately 27,777 e-h pairs.

It should be ruled out that when the electron hits the lateral reception surface (3), it describes a random trajectory and loses energy as it generates a free charge of pairs eh. This electron is finally completely absorbed by the substrate (2) at a distance that can be hundreds of micrometres away from the lateral receiving surface (3) that is to say from the point of impact. Therefore, each impacting electron ends up absorbed in some point in an area usually called interaction volume. This volume of interaction usually has the shape of a pear, as shown schematically in Figure 2 and Figure 3b, and its size depends on the initial energy of the electron.

More specifically, prior to impacting on the lateral receiving surface (3) said electron beam (10) passes through a mask (9) opaque to electrons, preferably made of platinum, with a slit that extends across the width of the sensor. electrons (1). More specifically, this groove has a width equal to the pitch between "pixels" of the input unit, and is preferably close to the lateral receiving surface (3), thus, the mask (9) defines the effective width of the " pixel "in the thickness direction of the substrate (2).

Preferably, as shown in Figures 1, 2 and 3a, the contact unit comprising a contact electrode (4) occupies substantially the entire width of the backplane (2p) and has a maximum height of 400 μm. Said contact electrode (4) is a deposition of doped silicon type p + designed to capture the free holes generated in the substrate (2) by the impact of said electron electron beam (10) and which are dragged by an electric field of polarization towards the backplane (2p).

Preferably, the guard unit comprises a guard electrode (5). The guard electrode (5) is deposited so that it extends across the width and length of the substrate (2), skirting the entire anterior plane (2a). Its geometry is substantially a set of strips in the manner of four strips forming a frame, wherein the side closest to the lateral receiving surface (3) has a plurality of slits. Said guard electrode (5) is a n-type doped silicon deposition with a height of 2 pm intended to capture the free electrons generated in the substrate (2) by the impact of said electron electron beam (10) and which are entrained by the electric field of polarization towards the previous plane (2a).

The input unit comprises a series of input electrodes (6) preferably of rectangular configuration and spaced from each other, to capture the concrete point of impact of the electrons of the electron beam (10) on the lateral receiving surface (3). Said entrance electrodes (6) are depositions of doped n-type silicon designed to capture the free electrons generated in the substrate (2) by the impact of said electron electron beam (10) and that are dragged by the electric field of polarization towards the previous plane (2a).

Specifically, the input electrodes (6) have a substantially rectangular configuration with a height of 10 to 70 pm and a width of 4 to 20 pm. More specifically, its upper plane is housed in said plurality of grooves of the guard electrode (5). Each of these input electrodes (6) are separated from the adjacent one by a distance comprised between 10 to 50 pm. It should be noted that each slit of the guard electrode (5) has a height of at least 1 μm and a width of at least 6 μm, where said width is always at least 1 μm greater than the width of the input electrode (6) that it lodges, so that they are never in direct contact, as can be seen in figure 3a.

On the other hand, the number of input electrodes (6) determines the spatial resolution of the electron sensor (1). Thus, in this embodiment preferably, the number of input electrodes (6) or "pixels" is equal to 2048, the width of each input electrode (6) is 10 μm and the height is 50 μm, and the separation between each central vertical axis of each entrance electrode (6) is 25 pm Therefore, the width of the electron sensor (1) is at least 51,200 pm It should be noted that these 2048 input electrodes (6) they have not been represented in their entirety in the figures to facilitate the understanding of them.

Preferably, the lower plane of each of the input electrodes (6), are housed in a plurality of receptacles of the base unit. That is, the base unit comprises a base electrode (8) with said plurality of receptacles partially covering each of the input electrodes (6).

More specifically, this base electrode (8) extends the entire width of the anterior plane (2a) and has a height between 100 and 400 μm. It should be noted that the size of these receptacles is variable, but preferably they have a substantially oval configuration with a height comprised between 10 and 150 pm, and a width comprised between 10 and 35 pm. Preferably, the base electrode (8) comprises a height of 200 μm, and each receptacle has a height of 50 μm and a width of 20 μm. Said base electrode (8) is a type n doped silicon deposition intended to capture the free electrons generated in the substrate (2) by the impact of said electron electron beam (10) and which are dragged by the electric field of polarization towards the previous plane (2a).

It should be noted that for each entrance electrode (6) the guard electrode (5) has a groove, and the base electrode (8) has a receptacle.

In this preferred embodiment, as shown in greater detail in Figure 3a, in the area of connection between each input electrode (6) and the base electrode (8), ie the area between the lower plane of the electrodes of input (6) and the upper plane of the base electrode (8), the electron sensor (1) comprises the energy measurement unit. This energy measurement unit in turn comprises an energy measurement electrode (7) for each input electrode (6). These energy measurement electrodes (7) increase the precision of the measurement of the energy of the electrons that pass through the series of input electrodes (6). Specifically, these energy measurement electrodes (7) are surrounded by the base electrode (8) and have a substantially oval shape with a height comprised between 10 and 20 pm, and a width comprised between 20 and 30 pm. Preferably, each energy measurement electrode (7) comprises a height of 20 μm and a width of 20 μm. Said electrodes of energy measurement (7) are depositions of n-type doped silicon designed to capture the free electrons generated in the substrate (2) by the impact of said electron of the electron beam (10) and which are dragged by the electric field of polarization towards the previous plane (2a). Thus, as shown in Figure 3b, the accuracy of the electron sensor is increased to measure the charge (and therefore the energy) generated in the substrate by the incident electrons (1).

More specifically in Figure 3b, the probability is shown that the electrons of the electron beam (10) are absorbed at different depths in the substrate (2). Additionally, this figure 3b shows by which electrode or electrodes (6, 7, 8) the charge generated by the electron along its trajectory through the substrate (2) will be detected. In this way, it can be verified how the electron sensor (1) detects with great precision where the electrons impinge by means of the input electrode (6). Additionally, this electron sensor (1) allows to measure the electron energy of the electron beam (10) by detecting the free charge of pairs eh generated at different depths, by means of the electrodes (6, 8), (7, 8) or ( 6,7,8). These electrodes (6, 7, 8) detect the depth and the lateral distribution to which the electrons are absorbed in the substrate (2), being both the depth and the lateral distribution proportional to the initial energy of the electrons.

It should be noted that the distance between each electrode (5, 6, 7, 8) of the previous plane (2a) is between 1 and 2 pm. More specifically, these separation zones are found in the following electrodes (5, 6, 7, 8):

- between each slit of the guard electrode (5) and each input electrode (6),

- between each guard electrode (5) and the base electrode (8),

- between each inlet electrode (6) and each receptacle of the base electrode (8),

- between each input electrode (6) and each energy measurement electrode (7),

- between each electrode of energy measurement (7) and each receptacle of the base electrode (8).

Additionally, the base electrode (8), each input electrode (6) and each energy measurement electrode (7) are connected, by means of metal tracks (13, 13 ', 13 ") usually of aluminum deposited on the substrate (2), to an electronic circuitry unit (12) inserted in the anterior plane (2a) of the substrate (2) following the base electrode (8), as shown schematically in Figure 4. Additionally, contact electrode (4) is also connected to the electronic circuitry unit (12) by a metal track not shown.

Said electronic circuitry unit (12) comprises an electric generator for generating a polarization voltage between the electrodes (5, 6, 7, 8) of the anterior plane (2a) and the contact electrode (4) of the posterior plane (2p) . Specifically, the electrodes (5, 6, 7, 8) are at a negative polarization potential with respect to the contact electrode (4). In this way, the polarization voltage generates an electric field that serves to drag the voids or free electrons of the e-h pairs generated in the substrate (2) to the backplane (2p) or to the front plane (2a).

More specifically, the free electrons of the pairs eh generated by the impact of an electron are dragged towards the electrodes (5,6, 7, 8) of the anterior plane (2a) and the holes are dragged towards the single contact electrode (4). ) of the backplane (2p) of the electron sensor (1). This movement of charges induces an electric current in the electrodes (4, 5, 6, 7, 8) that through metal tracks (13, 13 ', 13 ") deposited on the substrate (2) is measured in the electronic circuitry unit (12).

More specifically, the electronic circuitry unit (12) comprises at least one circuit electronic device for conditioning and processing the information captured by the electrodes (5, 6, 7, 8) by the impact of at least one electron of the electron beam (10) received on the lateral receiving surface (3).

Preferably, several electron sensors (1) are placed in parallel with different configurations to obtain different advantages, as well as to generate two-dimensional images formed by the successive addition of one-dimensional lines measured by each of the electron sensors (1).

The first configuration of several electron sensors (1) in parallel, is shown in Figure 5a, where three electron sensors (1) are separated from each other. Each of these electron sensors (1) has dimensions of the electrodes (4, 5, 6, 7, 8) optimized to detect a range of initial energies of the electrons of the electron beam (10). In this case, preferably for TEM microscopes, each of the electron sensors (1) is configured to detect respectively the following energy ranges of the electrons: 60-120 keV, 120-200 keV and 200-300 kV. In this way, depending on the energy used in a specific application, the use of a single electron sensor (1) can be selected to form the image (11).

The second configuration of several electron sensors (1) in parallel, is shown in Figure 5b, where two electron sensors (1) are positioned offset from each other at a distance of half a pixel to duplicate the spatial resolution. In this case both electron sensors (1) are used at the same time.

The third configuration of several electron sensors (1) in parallel is shown in Figure 5c, where at least two electron sensors (1) are placed in parallel, but preferably three. In this way it is possible to acquire images at a higher speed, ie at more frames per second, without reducing the exposure time by means of the "Time-Delay-Integration" technique that is applied with linear sensors in optical applications.This configuration is especially useful in applications that require the capture of two-dimensional series of images at high speed, such as in dynamic applications with TEM (in-situ TEM) microscopes.

The fourth configuration of several electron sensors (1) in parallel, is shown in the 5d, where at least two electron sensors (1) are placed in parallel and each of them comprises input electrodes (6) and / or energy measurement electrodes (7) with different sizes. This configuration allows to form the image (11) with different resolutions.

The fifth configuration of several electron sensors (1) in parallel, is shown in Figure 5e, where a plurality of electron sensors (1) are connected to form a two-dimensional image (11) by scanning the electron beam (10) successively in discrete steps and capturing with each electron sensor (1) a line of pixels in each position. That is, to form a two-dimensional image (11) of 2048 x 2048 pixels and if the electron sensor (1) comprises a line of 2048 input electrodes (6), it would be necessary to measure 2048 lines in 2048 discrete positions. The process is more efficient, preferably placing 3 electron sensors (1) with a separation of 512 pixels. In this way, the electron beam (10) would be scanned an equivalent distance of 512 pixels instead of 2048 pixels, and the capture of the two-dimensional image (11) would be done in a quarter of the time.

It should be noted that the present electron sensor (1) is capable of measuring a one-dimensional or two-dimensional image.

Preferably, to measure one-dimensional images typically when used in combination with a power filter, both the electron sensor (1) and the electron beam (10) projecting from the electron microscope are kept in the same horizontal position.

While at least four methods are used to measure two-dimensional images. In any of these methods, by means of capturing multiple projection lines of the electron beam (10) with the electron sensor (1), the two-dimensional image (11) is formed.

Preferably, in the first method, the electron sensor (1) is fixed at a position in the plane of projection of the electron beam (10), and the representation projected by the TEM is scanned by means of electromagnetic systems (e.g. projecting lens coils that are included in any TEM) that travel in a direction perpendicular to the linear direction of the sensor.

Preferably, in the second method, the projection of the electron beam (10) is in a fixed position, and the electron sensor (1) is moved by mechanical means such as the use of an electric motor with a mechanical system that transforms the rotation of the motor in a linear displacement. The advantage of this method is that it is not necessary to control the electromagnetic systems of the TEM for scanning the beam.

Preferably, in the third method, the projection of the electron beam (10) and the electron sensor (1) is in a fixed position, and the sample is displaced by mechanical means such as the use of an electric motor with a system mechanical that transforms the rotation of the motor into a linear displacement. The advantage of this method is that it is not necessary to control the electromagnetic systems of the TEM for scanning the beam or the sensor.

Preferably, in the fourth method, when the sensor is used as a sensor in EFTEM applications, the projection of the electron beam (10) filtered by an energy filter, the electron sensor (1) and the sample, are in a Fixed position, and the filtered electron beam is scanned in energy in the perpendicular direction of the electron sensor (1) using the electromagnetic systems present in the energy filters commonly used in TEM for spectrometry applications.

In another preferred embodiment, not shown, the electron sensor (1) is also applicable to measure the energy of transmitted and secondary electrons in the scanning electron microscopes in transmission mode, called STEM and SEM, by scaling the sensor size of the sensor. electrons (1) and the number and geometry of the pixels or electrodes (4, 5, 6, 7 8), to adapt it to these applications and the particular energy ranges of the application.

More specifically, in SEM and STEM applications the images the electron sensor (1) that we propose would be fixed in a position of the microscope since the images and spectra in these applications are formed by sweeping a point-to-point beam.

Claims (1)

R E I V I N D I C A C I O N S 1. Electron sensor (1) for electron microscopy performed by an electron microscope, wherein the electron sensor (1) comprises a substrate (2), with a front plane (2a) and a back plane (2p) parallel between yes, that is intended to absorb at least one electron of an electron beam (10) that crosses a sample and that is generated by the electron microscope, and this electron is capable of generating an electric charge of electron-hole pairs (eh) free on said substrate (2), characterized in that the voter sensor (1) comprises: - a lateral receiving surface (3), located on one of the sides of the substrate (2) to receive the electron beam perpendicularly (10), - a guard unit, with a lower plane and an upper plane, deposited in the anterior plane (2a) bordering parallel to at least the lateral receiving surface (3) traversed by the electron beam (10), to avoid leakage currents at the edge of the substrate (2), - a base unit, with a lower plane and an upper plane, deposited in the previous plane (2a) following the guard unit, designed to measure the electron energy of the electron beam that impact on the receiving surface lateral (3), - an input unit, with a lower plane and an upper plane, deposited in the previous plane (2a) between the lower plane of the guard unit and the upper plane of the base unit for detecting the point of electron beam electrons, - a contact unit, deposited in the backplane (2p), and - an electronic circuitry unit (12), located next to the base unit and linked to at least the base unit, the contact unit and the input unit, comprising an electric generator and electric circuit, wherein said electric generator generates an electrical polarization current, between the front plane (2a) and the backplane (2p), which drags the free electrons generated in the substrate (2) towards the base unit and / or the unit input, and drag the free holes to the contact unit; allowing the electrons and holes to be captured by their respective units and conditioning and processing the free electrons by an electronic circuit comprised in said control unit to form a one-dimensional or two-dimensional image (11) with a greater dynamic range. 2. - Electron sensor (1) according to claim 1, characterized in that the input unit comprises a series of input electrodes (6). - Electron sensor (1) according to claim 2, characterized in that the input electrodes (6) comprise a height between 10 and 70 pm, a width between 4 and 20 pm, and wherein said input electrodes (6) are separated from each other at a distance between their vertical axes between 10 and 50 p.m. 4. - Electron sensor (1) according to claim 3, characterized in that the input electrodes (6) comprise a height of 50 pm, a width of 10 pm, and are separated from each other at a distance between their vertical axes of 25 pm. 5. - Electron sensor (1) according to any one of claims 2 to 4, characterized in that the guard unit comprises at least one guard electrode (5) close to the lateral receiving surface (3), in whose plane bottom has a plurality of slits for receiving the upper plane of the input electrodes (6) without directly contacting. 6. - Electron sensor (1) according to claim 5, characterized the guard electrode (5) is deposited as four strips that form a frame, two of them across and two along the substrate (2) in wherein the strip of the guard electrode (5) closest to the lateral receiving surface (3) has a plurality of slits for receiving the upper plane of the input electrodes (6) without directly contacting it. - Electron sensor (1) according to any one of claims 5 to 6, characterized in that the guard electrode (5) comprises a height of 2 pm, and each slot has a height of at least 1 pm and an upper width at least 1 pm higher than the width of the input electrode (6). - Electron sensor (1) according to any of claims 2 to 7, characterized in that the base unit comprises a base electrode (8) with a plurality of receptacles in its upper plane to accommodate the lower plane of the electrodes of entrance (6) without contacting directly. 9. Electron sensor (1) according to claim 8, characterized in that the base electrode (8) extends the full width of the substrate (2) and has a height between 100 and 400 pm. 10. Electron sensor (1) according to claim 9, characterized in that the base electrode (8) comprises a height of 200 μm. 11. - Electron sensor (1) according to claim 8, characterized in that each receptacle of the base electrode (8) has a substantially oval configuration with a height between 10 and 150 pm, and a width between 10 and 35 pm. 12. - Electron sensor (1) according to claim 8, characterized in that each receptacle of the base electrode (8) comprises a height 50 pm and a width of 20 pm. 13. Electron sensor (1) according to any one of claims 8 to 12, characterized in that the junction zone between the lower plane of the input electrodes (6) and the upper plane of the base electrode (8) comprises a series of electrodes of energy measurement (7) to measure the energy of the electrons that when hitting on the lateral receiving surface (3) pass through the entrance electrodes (6). 14. Electron sensor (1) according to claim 13, characterized the energy measurement electrodes (7) have a substantially oval shape with a height between 10 and 20 pm, and a width between 20 and 30 pm. 15. Electron sensor (1) according to claim 14, characterized in that the energy measurement electrodes (7) comprise a height of 20 pm and a width of 20 pm. 16. - Electron sensor (1) according to claim 15, characterized in that each energy measurement electrode (7) comprises a superposition of measuring electrodes of a substantially oval configuration. 17. - Electron sensor (1) according to claim 1, characterized in that the contact unit comprises a contact electrode (4) that occupies substantially the entire width of the backplane (2p) and has a maximum height of 400 μm. . 18. - Electron sensor (1) according to claim 13, characterized in that the contact electrode (4), base electrode (8), each input electrode (6) and each energy measurement electrode (7) are connected, by means of metal tracks (13, 13 ', 13 ") deposited on the substrate (2), to the electronic circuitry unit (12) that is inserted in the previous plane (2a) of the substrate (2) below of the base electrode (8), 19. - Electron sensor (1) according to claim 16, characterized in that the contact electrode (4), the base electrode (8), each input electrode (6) and each electrode of the overlay of energy measurement electrodes they are connected, by means of metal tracks (13, 13 ', 13 ") deposited on the substrate (2) to the electronic circuitry unit (12) that is inserted in the previous plane (2a) of the substrate (2) following the base electrode (8). 20. System for electron microscopy performed by an electron microscope, characterized in that it comprises at least two electron sensors (1) according to any one of claims 1 to 17 placed in parallel to generate two-dimensional images formed by the successive addition of lines One-dimensional measurements by each of the electron sensors (1).